Vivek, On Mon, Sep 03, 2007 at 11:49:11AM -0400, [EMAIL PROTECTED] wrote: > Hi ! > > I am trying to use perfmon on Itanium 2 server (HP's testdrive td178 > machine ). I have a multi-threaded program but each thread can be pinned to a > different CPU (total 16 cores here). Each thread is going to monitor its own > overflow (i.e. receive its own overflow notification). For configuring this, > do i need to set PFM_FL_SYSTEM_WIDE while creating PFM_CONTEXT ? >
In system-wide perfmon requires that you create as many contexts and you have CPU core to monitor. That each context is loaded onto the right CPU core via pfm_load_context(). On IA-64 currently, you are using the v2.0 interface which has the PFM_LOAD_CONTEXT command. On this version, perfmon will pick the CPU used to mke the PFM_LOAD_CONTEXT call as the CPU to monitor. This means you need to ensure that you have pinned the caller thread to the right CPU core prior to making the call. Each context needs to be created with the PFM_FL_SYSTEM_WIDE flag set. > Currently, I am not setting this flag. I get multiple contexts fd's - each > per > thread, for each fd i use fcntl with F_SETOWN to give the creator thread the > ownership of that fd. Then i make each fd's asynchronous (using fcntl with > O_ASYNC) and use Linux's sideaffect mechanism of F_SETSIG to get individual > signals to each thread (i.e. for a file descriptor fd(x) created by > thread(x), thread(x) receives the SIGIO signal signalling the overflow). > The rest of the control flow remains identical to per-thread monitoring. So if you want to receive asynchronous notification with signal, you have to do as you described. > However, I observe that when running with 4 threads on 4 cores , one thread > hardly receives overflow notifications. Similarly, running with higher number > of threads(eg 16), only a few threads get overflow notifications and the > others get very little. What could be wrong here ? Is there anything i need > to do to program perfmon ? > Check that you are running on the right CPU before calling PFM_LOAD_CONTEXT. > PS : This mechanism used to work well when I was running with LinuxThreads (1 > thread = 1 pid model). I then always used getpid() instead of gettid(). > My current system however doesn't support LD_ASSUME_KERNEL environment > variable. So, I have to run it with NPTL threads now. > With NPTL, you need to use gettid() for the F_SETOWN call. > I have pfmon version 3.2 and i am using libpfm-3.1. kernel is 2.6.18 Your library seems a bit old. Why not use libpfm-3.2? -- -Stephane _______________________________________________ perfmon mailing list [email protected] http://www.hpl.hp.com/hosted/linux/mail-archives/perfmon/
